Researchers had previously located a binding protein on the outside of sperm called Izumol, but had -- until recently -- been unable to find the receptor protein on the egg. They had a baseball, but no glove.
To find Izumol's female partner protein, scientists at the Wellcome Trust Sanger Institute in Cambridgeshire, England, exposed mouse eggs to an artificial version of the Izumo protein and waited and watched for the magic to happen. Thus, the Juno protein was discovered.
"We have solved a long-standing mystery in biology by identifying the molecules displayed on all sperm and egg that must bind each other at the moment we were conceived," lead researcher Dr. Gavin Wright told The Telegraph.
To confirm their findings, Wright and his colleague bred mice to produce eggs without the alluring Juno protein. When inseminated, pregnancy proved impossibly. Researchers got the same results using Izumo-less sperm on healthy Juno-covered eggs. The findings were published this week in the journal Nature.
"Without this essential interaction, fertilization just cannot happen," Dr. Wright explained. "We may be able to use this discovery to improve fertility treatments and develop new contraceptives."
[Wellcome Trust Sanger Institute]